Many agricultural implements are relatively long or wide and needed to be folded or lifted to a more compact configuration for transport purposes so that the implement may be towed or moved along roads and paths through gateways. This is particularly evident in cultivating equipment such as harrows.
Agricultural implements employing lifting apparatus are described in U.S. Pat. Nos. 4,023,623; 4,116,282; 4,615,397; 4,328,869; and 4,355,690. The agricultural implements described in these specifications all employ hinged "winged frames" which are movable in a vertical plane extending generally transverse of the normal direction of movement of the implement. The winged frames are pivotted from a generally horizontally extending position to an upwardly extending position for transport purposes. U.S. Pat. No. 4,023,623 discloses a particularly relevant "winged hinged frame" and a hydraulic system for raising the frame. The implement described has a hydraulic cylinder pivotally mounted on the main frame. The winged frame is caused to pivot by the hydraulic cylinder applying a force to the winged frame via a linkage member which engages an abutment fixed to the main frame. The linkage member is pivotally attached to one end of the piston rod of the hydraulic cylinder, and is pivotally attached at its other end to the winged frame. The abutment engages the linkage intermediate its two pivot attachments. This particular device has the disadvantage that the linkage is subjected to considerable strain and would eventually fail due to the forces required to cause pivotting of the winged frame.
The lifting assemblies described in the above numbered U.S. patents include disadvantages in respect to the angle through which the "winged frame" may rotate. Their design generally inhibits rotation through an angle greater than 180.degree.. Still further, the hydraulic cylinders are coupled to the winged frames in such a manner that they are operated during normal use of the agricultural implement. This causes undue wear and stress on the hydraulic system. That is the winged frame is not permitted to "float" freely to adjust to the land contour without movement of the hydraulic cylinder.